Polyolefins generally require organic solvents or chemical modification either by oxidation or by malleation to make them water-dispersible which is necessary prior to emulsifying. The use of organic solvents, however, causes environmental concerns, and chemical modification of the polyolefins provides undesired end-use properties to formulated products incorporating the polyolefins and adds to the cost of the products.
U.S. Pat. No. 4,613,679 discloses emulsifiable polyolefin waxes prepared by reacting low molecular weight homopolymers and copolymers containing at least one alpha-olefin monomer having at least three carbon atoms with diesters of maleic acid in the presence of a free radical source. The grafting of the diesters of maleic acid onto poly-alpha-olefins is carried out in an inert atmosphere. The disadvantage of the process of U.S. Pat. No. 4,613,679 is that it requires malleation of polyolefins which modifies the end-use properties of the products due to change in molecular structure.
U.S. Pat. No. 3,644,258 discloses a method for preparing high solid latexes of olefin polymers which are prepared by: (1) heating a fluid, low-solids aqueous emulsion of the thermoplastic organic addition polymer in its alkaline salt form at a temperature between the softening point of the polymer and the point at which the polymer degrades while simultaneously lowering the pH of the emulsion to a value between 6.0-8.3 and (2) concentrating the emulsion to fluid latex with polymer content ranging about 40-65 wt %. The process requires acrylic monomers to be copolymerized with unsaturated olefins in the presence of free radical.
U.S. Pat. No. 3,919,176 discloses water-dispersible polyolefin compositions which are useful as hot melt adhesives. Such hot melt adhesives are prepared by using an esterified carboxylated polyolefin.
The disadvantage of the adhesive compositions disclosed in U.S. Pat. No. 3,919,176 is that the polyolefin undergoes chemical modification by a malleation process in the presence of free radical and neutralization by alkali to disperse in water.
U.S. Pat. No. 5,373,048 discloses an aqueous coating composition containing maleated polyolefins, a non-ionic surfactant, an amine and water which are emulsified. The aqueous coating composition disclosed in U.S. Pat. No. 5,373,048 provides poor adhesion to certain polymer substrates such as polypropylene.
There is a need for a non-halogenated, waterborne adhesion promoter to improve the adhesion of paints, inks and coatings to polymer substrates such as polypropylene, thermoplastic olefins, and polyethylene.